Thanks Oz. Good to have a discussion on the numbers.

i got my info from a metals industry publication - Fastmarkets Metal Bulletin - i can't copy the full article due to their copyright policy but here is some exerpts. Worth signing up for the latest industry info. I was probably a bit low on my TC if they are selling as non-standard spec based on below.

Zinc concs 'bloodbath' sees TCs reach new highs, lead terms dive

"Fastmarkets assessed the spot TCs for zinc concentrates at $210-230 per tonne basis cif China on December 28, the highest recorded since pricing began in December 2014."This comes soon after the production increase at the Dugald River mine, although fellow newcomer the New Century zinc mine continues to experience teething problems with its chemistry and concentrate grain size."

The switch from a tight to well-supplied zinc concentrates market has meant smelters are more discerning when it comes to which parcels they take. Material that has non-standard specifications is being bid at TCs as high as $300 per tonne with effectively no market for it currently. "